`
https://leetcode.cn/problems/factorial-trailing-zeroes/
`

/**
 * @param {number} n
 * @return {number}
 */
var trailingZeroes = function (n) {
  let res = 0;
  let divisor = 5;
  while (divisor <= n) {
    res += Math.floor(n / divisor);
    divisor *= 5;
  }
  return res;
};